1. Field of Invention
The present invention relates to a high definition digital audio-video data interface, and in particular, to a high definition digital audio-video data transmission device utilizing optical fiber as the transmission medium.
2. Related Art
In general, the high definition digital audio-video data interface includes a High Definition Multimedia Interface (HDMI), a Digital Visual Interface (DVI), and a forthcoming Unified Display Interface (UDI). Among them, the High Definition Multimedia Interface (HDMI) is utilized to integrate and standardize the transmission specification of the signals coming from the audio and video sources, so that in the design of a high definition digital audio-video system, the DVI is used as a basis in providing wider transmission bandwidth and a much more miniaturized connector. As such, only one single cable is required to transmit the uncompressed audio signal and high definition video signal, thus simplifying the installation of the audio-video system, and further raising the audio and video signals transmission quality. In this respect, the UDI is used as a PC digital display interface standard in compatible with the standard of HDTV signals. It is now replacing the gradually out-dated and phasing-out Video Graphic Array (VGA) analog standard, and thus in compatible with the DVI and the HDMI.
In this respect, the HDMI is taken as an example. To improve the performance of the transmission specification, a Transmission Minimized Differential Signaling (TMDS) coding is utilized by the HDMI. In general, TMDS is provided with a color data of three original colors (RGB)/intensity aberration (YPbPr) and a serial transmission loop of four channels (a connection) including a clock pulse channel. The respective channel utilizes the low amplitude differential transmission having 50 Ω terminal impedance and 0.15V voltage difference. The maximum transmission speed of the respective channel is 1.65 Gbps, thus ensuring the connection having transmission speed of 5 Gbps.
In addition, the HDMI is further provided with a support for the High Bandwidth Digital Content Protection (HDCP) mechanism, which is a kind of agreement reached and agreed upon jointly by the movie and program producers and the TV program transmission provider for protecting the intellectual property rights of the movie and TV programs, hereby preventing the illegal duplication of digital signal and image data. Meanwhile, the HDMI is used to provide better Display Data Channel (DDC) that is utilized to read the Extended Display Identification Data (EDID) indicating the displaying capability such as the resolution of the reception device. As such, password verification is performed between the transmission and reception device of the HDCP mechanism for the signals by making use of DDC, so that the transmission device and the reception device may verify each other at a predetermined time interval. In case that the verification fails, then the audio-video signals transmission is terminated immediately to protect the contents of the signals. In the signal transmission making used of HDMI, the transmission of Consumer Electronics Control (CEC) may optionally be utilized. Presently, in Europe, the audio-video equipment of communication habitually utilizes a cross-system remote-control transmission protocol called AV.Link, and in this connection, HDMI may be utilized in support of this standard protocol, thus achieving the control of a plurality of audio-video devices through a single remote controller.
For a more detailed description of the above-mentioned system, refer to FIG. 1. FIG. 1 is a schematic diagram of a framework of a transmission/reception system having a HDMI according to the prior art. As shown in FIG. 1, the transmission/reception system includes a transmission device 10 and a reception device 11 both having HDMI, with the former having a transmission unit 101, and the latter having a reception unit 111. In the transmission device 10 having HDMI, the audio-video data 601 to 603 are transmitted to the reception device 11 having HDMI through the transmission unit 101, and is received by the reception unit 111. The logic channels carrying these data are the first data channel 901, the second data channel 902, and the third data channel 903. In addition, a clock pulse channel 904 is responsible for transmitting a video pixel clock 604 to the reception unit 111, the frequency of which is utilized as a reference frequency for the return data. The above-mentioned four logic channels are operated in a simplex transmission mode, namely, they are used to carry only the data transmitted from the transmission unit 101, and received by the reception unit 111.
Moreover, the system is further provided with a DDC 905 and a Consumer Electronics Control (CEC) channel 906, that are used to read the Extended Display Identification Data (EDID) indicating the display capability such as the resolution of the reception device 11. In general, the DDC 905 is a logic channel, with its transmission specification in compatible with that of I2C Bus, and is usually utilized as a system management bus, including a Serial Data Line (SDA) and a Serial Clock Line (SCL), and are used to transmit the identification data of the reception device 11 and the reference clock pulses between the devices. Usually, the DDC 905 is operated in a half-duplex transmission mode, namely, both the transmission device 10 and the reception device 11 having HDMI may proceed with data transmission in both directions. However, at any one particular time interval, data may only be transmitted from the device on one side and received by the device on the other side.
In the conventional transmission/reception system having HDMI, the above-mentioned channels are realized by copper wires to achieve physical connection. However, for the application of this kind of copper wire, the major drawback is that it is susceptible to electromagnetic interference, mainly due to the limited bandwidth of the copper wire, and this kind of drawback constitutes an obstacle in the development of wider bandwidth transmission interface. Furthermore, usually, the signals transmitted in the copper wire are susceptible to power loss, so that the length of the transmission wire used for high definition multimedia interface may only reach 15 m at most. In the invention, optical fiber is used to replace copper wire to achieve physical connection in the framework of conventional transmission/reception system having HDMI, DVI, and UDI, thus overcoming and improving the shortcomings of the prior art utilizing copper wire.